Abstract:

A non-thermal plasma assisted combustion fuel injector that uses an inner
and outer electrode to create an electric field from a high voltage power
supply. A dielectric material is operatively disposed between the two
electrodes to prevent arcing and to promote the formation of a
non-thermal plasma. A fuel injector, which converts a liquid fuel into a
dispersed mist, vapor, or aerosolized fuel, injects into the non-thermal
plasma generating energetic electrons and other highly reactive chemical
species.

Claims:

1. A non-thermal plasma assisted combustion fuel injector, comprising:a.
an outer electrode and an inner electrode that provide surfaces to create
an electric field therebetween;b. a high voltage power supply to induce
said electric field;c. a dielectric material, operatively disposed
between said outer electrode and said inner electrode to prevent arcing
and promote said non-thermal plasma formation; and,d. a fuel injector
configured to convert a liquid fuel into a dispersed mist, vapor, or
aerosolized fuel;wherein a non-thermal plasma is created with the
electric field between the outer electrode and the inner electrode.

2. The non-thermal plasma assisted combustion fuel injector of claim 1,
where said inner electrode is configured as a basket.

3. The non-thermal plasma assisted combustion fuel injector of claim 1,
where said inner electrode is configured as a needle.

4. The non-thermal plasma assisted combustion fuel injector of claim 1,
where said inner electrode is configured as a brush.

5. The non-thermal plasma assisted combustion fuel injector of claim 1,
where said inner electrode is configured as a spiral wire.

6. The non-thermal plasma assisted combustion fuel injector of claim 1,
where said inner electrode is configured as a cone with electric
field-enhancing perforations throughout.

7. The non-thermal plasma assisted combustion fuel injector of claim 1,
where said inner electrode is configured as a cylinder with electric
field-enhancing perforations throughout.

8. The non-thermal plasma assisted combustion fuel injector of claim 1,
where said inner electrode is configured as a series of pointed washers.

9. The non-thermal plasma assisted combustion fuel injector of claim 1,
where said inner and said outer electrodes are made from material
selected from the group consisting of stainless steel alloys, tungsten,
tungsten alloys, refractory metals, carbon-based composites, carbon
nanotubes, and graphitic surfaces.

10. The non-thermal plasma assisted combustion fuel injector of claim 1,
where said dielectric material is selected from the group consisting of
alumina, porcelain, machinable glass ceramic, glasses, high temperature
plastics, polimides and polyamides, and rubber compounds.

11. The non-thermal plasma assisted combustion fuel injector of claim 1,
where said power supply operates in a range of about 1 to 50 kV and of
about 10 Hz to 20 kHz.

12. The non-thermal plasma assisted combustion fuel injector of claim 1,
where said inner electrode and said outer electrode are spaced apart in a
range of about 0.5 mm to 20 mm.

13. The non-thermal plasma assisted combustion fuel injector of claim 1,
where said outer electrode is configured in a conical shape.

14. The non-thermal plasma assisted combustion fuel injector of claim 1,
where said outer electrode resides within said dielectric material.

16. The non-thermal plasma assisted combustion fuel injector of claim 1,
where said non-thermal plasma assisted combustion fuel injector is
mounted in a cylinder head configuration.

17. (canceled)

18. (canceled)

Description:

FIELD OF THE INVENTION

[0002]The present invention relates generally to non-thermal plasmas, and,
more particularly, to the use of non-thermal plasmas in the design of a
fuel injector that feeds internal combustion engines or other combustion
devices employing fuel injectors.

BACKGROUND OF THE INVENTION

[0003]The present invention is a device that employs electrical
discharges/non-thermal plasmas in a gaseous medium to activate a fuel
derived from a fuel injector to promote more effective and efficient
combustion. In non-thermal plasmas, the electrons are `hot`, while the
ions and neutral species are `cold`--which results in little waste
enthalpy being deposited in a process gas stream. This is in contrast to
thermal plasmas, where the electron, ion, and neutral-species energies
are in thermal equilibrium (or `hot`) and considerable waste heat is
deposited in the process gas.

[0004]The present invention utilizes a type of electrical discharge called
a dielectric barrier discharge (DBD) or silent discharge plasma (SDP) to:
1) break up large organic fuel molecules into smaller ones that are more
easily and completely combusted; and 2) create highly reactive
free-radical chemical species that can promote more efficient combustion
by their strong "redox" power (fuels become strong reducing agents,
oxygen becomes more oxidizing) or by their ability to promote
combustion-sustaining chain reactions or chain reactions that further
generate active species. This device is envisioned for application to a
variety of internal combustion engines, such as automobile engines and
all turbine engines that normally employ fuel injectors.

[0005]U.S. Pat. No. 6,606,855, Plasma Reforming and Partial Oxidation of
Hydrocarbon Fuel Vapor to Produce Synthesis Gas And/Or Hydrogen Gas, by
Kong et al., teaches methods and systems for treating vapors from fuels
with thermal or non-thermal plasmas to promote reforming reactions
between the fuel vapor and re-directed exhaust gases to produce carbon
monoxide and hydrogen gas, partial oxidation reactions between the fuel
vapor and air to produce carbon monoxide and hydrogen gas, or direct
hydrogen and carbon particle production from the fuel vapor. However, a
problem with the reactions taught in Kong et al. includes the fact that
hydrocarbon gases, when formed, are accompanied with carbon particles
(ie. Soot). Introduction of carbon particles into a working engine is
considered undesirable due to the engine damage that can be caused and,
in particular, the difficulty in combusting the carbon particles.

[0006]In contrast, the present invention is a specific non-thermal plasma
fuel injector, designed to make free radicals and more easily-combusted
cracked species of out of injected fuel to enhance combustion with no
formation of soot. There are no oxidative reactions as in Kong et al. and
only fuel is treated, not O2 or exhaust gases as described in Kong et al.

[0007]U.S. Pat. No. 6,322,757, Low Power Compact Plasma Fuel Converter, by
Cohn et al., also teaches the conversion of fuel, particularly into
molecular hydrogen (H2) and carbon monoxide (CO). The invention of
Cohn et al, like Kong et al., suffers from rampant soot production, as
well as electrode erosion (because the Plasmatron converter actually
employs a hot-arc, thermal plasma, rather than a low-temperature,
non-thermal plasma). Further, it is not clearly evident that molecular
hydrogen is the key promoter of more stable/complete combustion.

[0008]Various objects, advantages and novel features of the invention will
be set forth in part in the description which follows, and in part will
become apparent to those skilled in the art upon examination of the
following or may be learned by practice of the invention. The objects and
advantages of the invention may be realized and attained by means of the
instrumentalities and combinations particularly pointed out in the
appended claims.

SUMMARY OF THE INVENTION

[0009]In accordance with the purposes of the present invention, as
embodied and broadly described herein, the present invention includes a
non-thermal plasma assisted combustion fuel injector that uses a first
and second electrode to create an electric field from a high voltage
power supply. A dielectric material is operatively disposed between the
two electrodes to prevent arcing and to promote the formation of a
non-thermal plasma. A fuel injector, which converts a liquid fuel into a
dispersed mist, vapor, or aerosolized fuel, injects into the non-thermal
plasma generating energetic electrons and other highly reactive chemical
species.

[0010]In another embodiment, the present invention includes a method for
cracking fuel using a fuel injector to create a fuel mist and then
subjecting the fuel mist to a non-thermal plasma created between an outer
electrode and an inner electrode, thereby cracking the fuel mist and
creating fuel fragments

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]The accompanying drawings, which are incorporated in and form a part
of the specification, illustrate the embodiments of the present invention
and, together with the description, serve to explain the principles of
the invention. In the drawings:

[0023]The present invention uses a silent-discharge/dielectric-barrier
non-thermal plasma (NTP) reactor to generate energetic electrons and
other highly reactive chemical species (such as free radicals) in a fuel
that feeds internal combustion engines, or other combustion devices
employing fuel injectors. The highly reactive chemical species: 1) break
up large organic fuel molecules into smaller ones that are more easily
and completely combusted; and 2) create highly reactive free-radical
chemical species that can promote more efficient combustion through
enhanced reactive power, ability to promote combustion-sustaining chain
reactions, and follow on chain reactions that generate more active
species.

[0024]Referring now to FIG. 1, NTPs can be created by several types of
electric discharge configurations known to those skilled in the art. In
the present invention, the reactor makes use of a dielectric-barrier
discharge arrangement. Here, two conducting electrodes, outer electrode
10 and inner electrode 20, one or both of which are covered by a
dielectric material, are separated by gas-containing gap 30. Gap 30 may
range from about 0.5 mm to 20 mm.

[0025]Dielectric materials that may be used include, but are not limited
to: dielectric ceramics such as alumina, porcelain, Macor® machinable
glass ceramic, glasses of various types, high temperature plastics such
as Teflon®, polimides and polyamides, dielectrics such as those used
in capacitors (e.g. Mylar® and Kapton®--DuPont Company), and
rubber compounds.

[0026]Materials used for the electrodes may include, but are not limited
to: conductive, corrosion-resistant metals, such as stainless steel
alloys, tungsten and tungsten alloys, and any other refractory metals and
alloys that are resistant to erosion in the plasma environment; and,
carbon-based composites, carbon nanotubes, and graphitic surfaces, which
are particularly resistant to etching in plasma environments (such as
those used in plasma television electrodes or other related
applications).

[0027]One or both electrodes must be shielded from the other electrode by
a dielectric material so that arcing is avoided and streamer formation (a
streamer is a fast-time microdischarge characteristic of DBDs) is
induced, i.e. a dielectric plasma is made. Electrodes can be made with
sharp points, roughness or edges to enhance high field concentrations so
as to aid breakdown and thus plasma initiation

[0028]A high-voltage source sufficient to electrically break down (i.e,
make conductive, make a plasma) the fuel (typical range of 1 kV to 50 kV,
depending on the fuel and the gap spacing) (alternating current,
frequency in a typical range of 10 Hz-20 kHz; or voltage pulse) is
applied to electrodes 10 and 20 creating electrical-discharge streamers
in the gas passing between. An inverter and step-up transformer produces
the high voltage that boots the 12 V DC battery supply in a typical
automotive electrical system, to the required voltage. Such circuits can
be made very small and lightweight, using today's advanced semiconductor
switching inverter/converter circuits.

[0029]The discharges are the source of the active non-thermal plasma. The
embodiment presented here is a cylindrical, coaxial dielectric barrier
discharge/silent discharge plasma (DBD/SDP) reactor, however, other
arrangements (e.g., planar, rectangular) may also be employed by one
skilled in the art. Additionally, other embodiments utilizing clusters of
reactors can also be employed by on skilled in the art. The wave form of
the alternating current can be sine, square, or complex, so as to aid
plasma initiation by the applied voltage rise time, and to promote
electrode self-cleaning that is aided by the breakdown follow-on wave
shape.

[0030]Referring now to FIG. 2, a cross section of one embodiment of the
plasma assisted combustion fuel injector device (PACFI), pintle needle
valve 40 is opened and closed by activation of solenoid 41 through input
wires 42. Spring 43 returns valve 40 to the closed position when solenoid
41 is not energized. When valve 40 is open, fuel from hose connection 44
sprays out as an atomized mist 45 into conical chamber 46. A nonthermal
plasma is created within conical chamber 46 by the input of a high
voltage alternating current through power wires 39 that are connected to
the external "basket" electrode 47 and outer electrode 48 that resides
within insulator block 49. Insulator block 49 is made from a dielectric
material.

[0031]Referring also now to FIG. 3, where the inner electrode
configuration is basket electrode 47 that is composed of wire hoop 50
connected with vertical wires 51 to larger diameter wire hoop 52
(additional wire hoops may also be employed between 50 and 51). Basket
electrode 47 is suspended from insulator block 53 by horizontal support
wires 54. The open structure of basket electrode 47 allows atomized mist
45 essentially unrestricted passage and yet provides the electrode
surface required to generate the nonthermal plasma.

[0032]Other inner electrode configurations provide electric field
enhancement within gap 30 so as to reduce the power required to generate
the required strength of non-thermal plasma. FIG. 4a is an embodiment
where inner electrode 100 is configured in an array of wires in a tapered
"brush" configuration. FIG. 4b is an embodiment where inner electrode 110
is a spiral wire. FIG. 4c is an embodiment where inner electrode 120 is a
cone with electric field-enhancing perforations throughout. FIG. 4d is an
embodiment where inner electrode 130 is a cylinder with electric
field-enhancing perforations throughout. FIG. 4e is an embodiment where
inner electrode 140 is a series of pointed washers. All of the
aforementioned inner electrode embodiments may be made from stainless
steel, copper, tungsten, tungsten alloys, refractory metals, and
carbon-based composite.

[0033]A dielectric barrier electrode configuration creates high-energy
streamers that produce both intense ultra violet light and strong
electric/magnetic fields that are more effective in generating cracked
(i.e. lower molecular weight), chemically different fuels, compared to a
corona discharge processes. Thus, for example, a residual gas analyzer
looking at the effect of plasma cracking of propane shows that methane
sized free-radical fragments is created by the present invention.
Methane, being of lower molecular weight, burns at a higher rate than
does propane, and, thus, more efficiently. Thus, lower quality fuels may
be used to replace previously necessary high-grade fuels, e.g. use diesel
fuel in a jet engine in lieu of Jet A.

[0034]By improving the burning propensity of fuels by converting them to
smaller compounds, it is now possible to dilute the combustion mixture
with more air than was possible with prior art inventions. Increasing
dilution with air improves reduction in the amount of nitrogen oxides
(NOx) that is created by dropping the overall combustion temperature.
Thus, there are at least three important results provided by the present
invention: first, less fuel is consumed due to the enhanced combustion
efficiency; second, there is a reduction in the number of unburned
hydrocarbons; and third, lower amounts of oxides of nitrogen produced.

Testing

[0035]Referring now to FIG. 5, graphically showing the results of testing
the center electrode 100 embodiment shown in FIG. 4a. Non-thermal plasma
created in the gap between the brush center electrode and the dielectric
cone decomposes ("cracks") the atomized liquid fuel into simpler
hydrocarbons. For this test, the PACFI unit was mounted inside a clear
plastic (polycarbonate) enclosure that allowed: isolation of the
high-voltage unit, observation of the injector spray pattern, and
collection of residual fuel. Iso-octane (a common surrogate for gasoline)
was used as the input fuel.

[0036]The test was conducted in two stages: first, fuel was injected
without a nonthermal plasma present and analyzed with a residual gas
analyzer; second, fuel was injected with a nonthermal plasma present and
analyzed with a residual gas analyzer. The results were then compared to
determine the distribution of products with and without the influence of
the plasma.

[0037]An electric fuel pump was used to, delivered liquid iso-octane to
the fuel injector at a pressure of about 80 psig. While injecting the
iso-octane (8 pulse shots), the resulting iso-octane spray mass spectrum
coming out of the PACFI unit was measured using a residual gas analyzer.
The mass peaks that were obtained were then compared with reference
mass-spectral data to confirm the signature peaks for iso-octane. Common
signature mass peaks, such as M29, M41, M43, and M57, were observed,
appearing in the measuring range from 1 to 65 amu of the instrument.

[0038]In the second stage, the plasma reactor was activated using a power
supply with an AC frequency of 566 Hz and voltage of 10±0.5 kV. The
delivered nonthermal plasma power was about 2±0.5 W. Pressurized
iso-octane was again sprayed from the injector and analyzed with the
residual gas analyzer, providing the mass spectrum of a sample collected
from the chamber. The test was repeated twice more, providing a total of
three datasets for fuel only runs and three datasets for fuel with
nonthermal plasma runs. These six datasets are normalized to the signal
of mass 28 (nitrogen) in order to provide a simple means of comparing the
strengths of the peaks on a common scale.

[0039]FIG. 5 shows two averaged datasets, one for a fuel only run (shaded)
and one for a fuel with plasma run (closed circles). With just 2 W of
plasma power, increased iso-octane fragment peaks are observed especially
for the lower mass peaks M15, M27, M29, M39, M41, M43, M56, and M57. For
example, the molecular formula of M29 is CH2-CH3. The increased
M29 implies that the plasma cracked the iso-octane and produced more
CH2-CH3, which is an easily burnable species. The fact that
significant increases in these lower-mass peak signals were observed in
the presence of the plasma confirms that the PACFI unit cracks the
more-complicated hydrocarbon gasoline-surrogate (iso-octane) into smaller
fragments. Furthermore, because there is very little change in the M2
peak (hydrogen) with the plasma, our invention is distinguished from
those prior art inventions taught in Cohn et al., and Kong et al., which
are fuel converters (mainly to hydrogen), rather than fuel "crackers" and
active-species producers.

[0041]Referring now to FIG. 6 showing is a cross section of an internal IC
engine port fuel injection configuration for mounting the PACFI. Here,
the PACFI is a direct replacement for a conventional fuel injection
device, but has additional wiring to supply the high voltage AC to drive
the plasma component. PACFI 60 is mounted in port 75 of intake manifold
70 and sprays the plasma treated fuel mist in the direction of intake
valve 65.

[0042]Referring now to FIG. 7, showing a direct injection configuration
that is quite similar to a diesel engine's configuration. PACFI 80 is
mounted in cylinder head 85 of the engine and is centrally located so
that the plasma treated fuel is directed down into engine cylinder 88.
Note that use in a diesel engine would require a higher-pressure PACFI
device as the fuel is continuously injected during combustion.

[0043]The foregoing description of the invention has been presented for
purposes of illustration and description and is not intended to be
exhaustive or to limit the invention to the precise form disclosed, and
obviously many modifications and variations are possible in light of the
above teaching.

[0044]The embodiments were chosen and described in order to best explain
the principles of the invention and its practical application to thereby
enable others skilled in the art to best utilize the invention in various
embodiments and with various modifications as are suited to the
particular use contemplated. It is intended that the scope of the
invention be defined by the claims appended hereto.